[R] select the last row by id group

[Dimitrios Rizopoulos]

one approach is the following:

math <- c(80, 75, 70, 65, 65, 70)
reading <- c(65, 70, 88, NA, 90, NA)
id <- c('001', '001', '001', '002', '003', '003')
score <- data.frame(id, reading, math)
#############
ind <- cumsum(tapply(score$id, score$id, length))
score[ind, ]


I hope it helps.

Best,
Dimitris

---- 
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


Quoting Tony Chu <gatony at gmail.com>:

>   Dear R users:
> 
>   I have a small test dataframe as the follows :
> 
> math = c(80,75,70,65,65,70)
> reading = c(65,70,88,NA,90,NA)
> id = c('001','001','001','002','003','003')
> score = data.frame(id, reading, math)
> 
> > score
>    id reading math
> 1 001      65   80
> 2 001      70   75
> 3 001      88   70
> 4 002      NA   65
> 5 003      90    65
> 6 003      NA   70
> 
>   Could someone advise me tips about how to select the last row from
> each id group of 001, 002, & 003?
> 
> In other words, the rows I need are :
> 
>    id reading math
> 3 001      88   70
> 4 002      NA   65
> 6 003      NA   70
> 
>  I tried function sebset but could not go very far. Thanks !
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
> 
> 


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm